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8.4.4 Managing Ramp Demands

At times during ramp metering operation, the traffic demand on some ramps may not be satisfied. This could occur during the peak hour when mainline flows are at their highest such that the metering is at its most restrictive. At the same time, arrival flow on the ramp may also be at its peak and be greater than the maximum permissible metering rate. The result is residual queuing on the ramp which may overspill onto the adjoining arterial roads if inadequate storage is provided in design.

Where long queues during ramp metering operation are anticipated and cannot be avoided during design, consideration should be given to measures that provide for the queue overflow on the arterial road. In practice, with coordinated ramp metering strategies in place, ramp demands over a group of ramps can generally be satisfied for a longer period due to the balancing of queues.